Annual herb forming mats to 1 m wide Stem: prostrate, branched from the base, and hairy. Leaves: opposite, pinnately compound, short-stalked, 2 - 6 cm long. Leaflets usually in pairs of six to eight, 0.5 - 1.5 cm long, oblong. Flowers: solitary, in axils, on 0.5 - 1 cm long stalks, yellow, to 1 cm wide. Sepals awl-shaped. Ovary five-chambered. Stamens two to three times as many as petals. Fruit: dry, indehiscent, splitting into five segments, to 1 cm wide, spiny, with tuber-like projections. Each segment divided into three to five one-seeded compartments.

Similar species: No information at this time.

Flowering: mid-June to late September

Habitat and ecology: Introduced from Europe. Local along unpaved roads and streets, and in the parking lots of towns with sandy soil. It has also been found along railroads and in sandy cultivated fields.

Occurence in the Chicago region: non-native

Etymology: Tribulus is the Latin name for a caltrop, referring to the spiny fruit of this plant. Terrestris means terrestrial.